Hello Ckowheero25
Our dear collegue @Danhiel was totally right. You need a ticket from the last stop in the Mobilis tarif network to the first stop in the Unireso fare network. And this, if you travel using regional trains that do stop at these two places.
If you take the IR, you have to get a ticket from Nyon to Geneva and v.v., provided the train stops at these places.
See paragraph 2.5.2:
Les titres de transport communautaires sont valables jusqu’au dernier point d’arrêt ou dès
le premier point d’arrêt conformément à l’horaire, situé dans les zones de la CTV
mentionnées sur le titre de transport.
https://www.mobilis-vaud.ch/wp-content/uploads/2021/08/T651.22_15.12.2024.pdf
And please, don’t elaborate the mindset that everything has to be free of charge; you won’t be working without a salary in future, do you? Everything has a value, even the public transit; currently, it is now paid by others for you.
Kind regards,
Roland